Frequently Asked Questions
Is there a glossary where I can learn what these
closed captioning terms mean?
Since it is updated
frequently and too long for this FAQ, please refer to this
glossary page:
http://cpcweb.com/caption-service/glossary.htm
What is captioning?
Captioning is text that
appears on a video, which contains dialogue and audio cues such
as music or sound effects that occur off-screen. The purpose of
captioning is to make video content accessible to those who are
deaf or hard of hearing, and for other situations in which the
audio cannot be heard due to noise or a need for silence.
Captions can be either open (always visible, aka "burned
in") or closed, but closed is more common because it lets each
viewer decide whether they want the captions to be turned on or
off. Closed captions are transmitted as a special coded signal
sent along with the video picture, and require a decoder in your
television or cable box to see them (most TVs and cable boxes
do). This special signal is what broadcasters check for to
ensure that your video is in accordance with the law. Captions
typically have the appearance of white, mono-space text on an
opaque black background.
What is Subtitling?
Subtitling is text that appears on a video and
typically contains only a transcription (or translation) of the
dialogue. Subtitle tracks which also contain non-verbal audio
cues are called "SDH" (Subtitles for the Deaf and Hard of
hearing) tracks.
Often, subtitles are burned into the video
so they can't be turned off, although DVD and Blu-ray (and a few
other formats) can contain multiple tracks of subtitles which
can be selected and turned on or off by the player. Subtitles
vary in appearance and have more fonts and colors available than
captions. Subtitles are required by law in many European and
Asian broadcast markets.
Why is closed
captioning necessary, or why should I bother with it?
The FCC requires the majority of programming seen on
broadcast TV in the United States to be closed captioned. The
CRTC requires the same for Canadian broadcasts. Many other
countries have their own requirements as well. Section 508
regulations contain stringent captioning requirements (including
captioning for webcasts) for the Federal government and
organizations that receive funding from the Federal government,
which includes most academic institutions. The ADA requires that
videos be accessible to the deaf and hard of hearing in public
accommodations and other public venues, such as hotels and
stadiums. Captioning is an ideal way to make video accessible.
Even if your program is not being broadcast or is otherwise
exempt from the closed captioning requirements, keep in mind
that over 10% of the population is deaf or hard of hearing. If
you do not caption, you will not reach this audience. Closed
captioning is also used by a large number of non-native language
speakers to help them better understand the programs they watch.
If you do not caption your videos, you are missing out on a huge
portion of your potential market.
What are the
basic steps needed to closed caption a video?
The
first (and usually most time consuming) step is to get a
transcript of your video, which contains all of the dialogue as
text, as well as the non-verbal audio cues.
For post
production captioning (not live), the next step is called time
stamping or synchronization, in which each caption line or cell
is synchronized to the appropriate in and out time to match up
with the video. Modern software makes this step very easy, and
it can often be finished faster than real time. There is no need
to struggle with manually entering time codes by hand, or
dragging in/out points around on a timeline.
Finally, the
captions need to be encoded, or converted from text and
formatting information into the special code that is used for
broadcast. The encoding used to be exclusive to legacy
tape-to-tape hardware encoding systems, but recently, software
encoders that works with your NLE software or video server have
become available. This encoded data must then be properly merged
into the video signal or data so that it can be transmitted
along with the video.
How do I transcribe a video
for closed captions and/or subtitles?
If you already
have a shooting script, lecture notes, etc., these can be used
to partially or completely eliminate the need to transcribe the
video. If you don’t have a script at all, the fastest way to get
a transcript (and the most popular option for live captioning)
is to use a professional stenographer (like a court reporter)
who has the specialized skill to operate a steno machine,
allowing them to type much faster than on a regular keyboard.
Because this is a special skill that takes years of training,
stenographers tend to charge a lot of money. Another option used
for live captioning is a shadow speaker, who listens to what is
being said by all voices in the video and repeats them in
his/her own voice, using a speech recognition system (see below)
to turn the speech into text.
Aren’t there any
speech recognition systems to automatically transcribe my video?
As of November 2009, there are no commercially available speech
recognition systems which can simply take a finished video and
transcribe all of the speech into text with enough accuracy for
intelligible closed captioning. The automatic speech-to-text
systems that do exist are not yet reliable or accurate enough.
Universal speech-to-text is an extremely difficult problem
despite many years of research.
Software is available which
can recognize a single speaker’s speech with good accuracy, as
long as that speaker first trains their voice into the system,
dictates clearly, and there is no background noise or music.
These systems are sometimes used for captioning live broadcasts
in smaller markets, where hiring a stenographer would be too
expensive. When the video contains multiple voices, a shadow
speaker is used. This is a person who listens to everything that
is said in the video, and repeats it in his/her own voice, like
a language interpreter but without changing the language. This
allows the speech recognition software to be tightly trained
onto the shadow speaker’s voice patterns, enabling reasonably
good accuracy (up to 90-95% with experience).
Are closed captions simply composed of text and time codes?
Closed caption data consists of a complex, multi-threaded stream
of control codes, commands, and text and timing information. The
proper encoding of this stream, and insertion of the data into
the proper location in the video signal, is part of what makes
closed captioning data difficult to work with.
What are the differences between closed captions and subtitles?
The main difference is that subtitles usually only transcribe
the spoken dialog, and are mainly aimed at people who are not
hearing impaired, but lack fluency in the spoken language.
Closed captions are aimed at the deaf and hearing impaired, who
need additional non-verbal audio cues (such as "[GUN SHOT]" or
"[SPOOKY MUSIC]") to be transcribed in the text. Closed
captions are also useful for situations in which video is being
shown but the sound is muted or difficult to hear, such as for a
noisy bar, convention floor, video signage & billboards, etc..
Subtitles which also contain these non-verbal cues are
usually referred to as "SDH" (Subtitles for the Deaf and Hard of
hearing) tracks, but for various reasons, closed captions are
usually the preferred method of making video accessible for the
deaf and hearing impaired. SDH subtitles tend to be used on
video formats that do not support closed captioning, such as Blu-ray
discs.
Another difference between closed captions and
subtitles is that closed captions are transmitted as an encoded
stream of commands, control codes, and text. Because it is text,
it can be turned on and off at the viewer's discretion. Many TVs
allow you to choose how the text is rendered on the screen
(extra large, extra small, transparent, etc.) It also means that
the text can be decoded and edited or converted to other
formats. On the other hand, subtitles are carried as bitmap
images so the font and size is pre-determined and cannot be
changed by the display device, and because they are images not
text, they cannot easily be decoded back into text form or
converted to other formats.
For those delivering their video
for broadcast, perhaps the most important difference between
captions and subtitles is simply that closed captioning is
required by the FCC/CRTC, and your video cannot be broadcast or
distributed unless the closed captioning data is present.
Subtitles (even SDH subtitles) do not satisfy these
requirements.
Why has closed captioning
traditionally been so difficult?
Closed captioning
has often been considered only as an afterthought, not only for
editors and production facilities, but also for hardware and
software manufacturers. Different video systems had to invent
different workarounds in order to support closed captioning, so
there are a huge variety of different workflows needed to
support all the various formats and systems that are out there,
and many “gotchas” that can disrupt an otherwise smooth
workflow. Also, most NLE programs and video conversion and
compression programs were not designed to support closed
captioning at all, so different “tricks” are needed in order to
make it work. Often, any processing or conversion done to a
video will strip out the closed captions. A huge amount of R&D
has been necessary to find, support, and document all of the
various workaround and tricks that are specific to each format
or system.
Fortunately, advances in end-user software
workflows are slowly but steadily helping to reduce the
complexity of closed captioning, such that it is now practical
for most editors with modest NLE systems to do their own
captioning, even in HD.
Why was closed captioning
traditionally considered to be expensive?
Closed
captioning had traditionally been expensive because very
expensive decks and legacy hardware encoders were needed, and
because it was a linear process, this gear would be tied up for
a considerable length of time when doing the captioning. Also,
because closed captioning (especially for HD) required a lot of
specialized video engineering knowledge, running a captioning
system was previously seen as a high-end endeavor limited to the
best equipped production facilities.
However, recent advances
in software encoding for popular NLE systems have drastically
reduced the cost of entry and resources needed to do closed
captioning in-house.
The bulk of the closed captioning work
occurs in the transcription step, in which the dialogue and
audio cues of the program have to be entered as computer text.
This step is very labor intensive. Having a script (shooting
script, notes, etc.) can drastically cut down the time needed
for this step. Doing it in-house may be time consuming but can
also save a lot of money.
Why was closed
captioning traditionally done by service companies instead of
in-house?
In the past, it was not feasible for most
facilities to bring closed captioning in-house, due to the very
high cost of the necessary hardware and software, as well as
specialized training needed to run the system. However, recent
advances in affordable and easy to use closed captioning
software encoders (which eliminate the need for expensive
hardware) have made it possible for anyone to do their own
closed captioning, right from their NLE system.
What are the advantages to bringing closed captioning capability
in-house?
Captioning in-house can save a lot of
money if you have a large volume video that needs to be
captioned. It also saves time and money because you do not need
to print to tape and ship it to a 3rd party service company,
then wait for them to ship the tape back. Since you’re doing it
all in-house, you have full control over quality and can inspect
the results and make necessary changes immediately. There is no
risk of losing your master or having the project be delayed due
to shipping problems or damaged tapes.
If you need extremely
fast turnaround or the ability to make last minute changes (such
as editing and delivering a show same day), having captioning
capabilities in-house can save the very high costs of hiring a
real-time captioner. Another common scenario is when you need to
deliver multiple versions of a program for different markets.
Doing this in house can save a lot of money in tape stock and
captioning fees.
I already use a service for my closed
captioning, and I’m not interested in doing the captioning
in-house. Why should I consider adding captioning capability to
my facility?
Even if you use a service for the bulk of your
captioning needs, having the ability to edit and convert closed
captions in-house can be extremely useful. For example, if you
need to make a last minute edit or correction, you will be able
to fix up the captions without having to print a new
un-captioned tape and wait several days turnaround (and pay
fees) for the service company to make a new captioned master. If
you need multiple versions of a program for different markets,
you can have the service company do the bulk of the captioning
work and make the small changes yourself, without incurring
additional fees. It will also allow you to re-use and convert
closed captions you have done on past projects. For example, if
you want to take a captioned tape from your library and
re-master it for DVD, Blu-ray, or the web, you can convert the
closed captions on the master into captions or subtitles for any
other delivery method.
How do I effectively ask
questions about closed captioning?
To figure out the
right workflow for successfully captioning your video, the most
important factors are what format you need to deliver in, and
what kind of system you are using to create or convert to that
format. If it is a tape format, then the specific deck and the
hardware interface between the source and the deck come into
play. If it is a file format, then not only the specifics of the
file format are important, but also on the receiving end, it is
important to know what kind of system will be used to read or
play back the file. Since caption data is fragile, it usually
does not survive format conversions or transcoding unless
special care is taken, and many video systems and programs were
not designed to read or preserve the closed captions at all.
An example of a unhelpful way to ask a closed captioning
question:
“How do I closed caption my video?”
“How do I
caption a XYZ file?”
“Help! My captions aren’t working!”
A
better way to ask a question, and more likely to get a useful
response:
“I’m using ‘ABC’ NLE software (version 1.2) with a
‘XYZ’ video capture card. My timeline is in the ‘QRS’ codec. How
do I output to ‘BCD’ tape with closed captions?”
“I’m using
‘JKL’ captioning software, and I’m losing the first caption that
should appear after each edit point in my timeline. How can I
fix this?”
DVD/Blu-ray
What kind of
closed captioning and/or subtitling is supported by DVD?
DVD
supports both NTSC closed captioning (CC1-CC4) and subtitles (32
tracks). In the case of closed captioning, the captions are
usually decoded and displayed by the TV, so they are controlled
using the TV’s menu or remote. Subtitles are controlled by the
DVD player and can be turned on/off with the player’s remote or
by commands in the DVD menus. DVD does not support Teletext,
which is the PAL standard for closed captioning.
What
kind of closed captioning and/or subtitling is supported by Blu-ray?
Blu-ray currently supports subtitles only. There is no
specification for adding closed captions to Blu-ray discs. For
this reason, most commercial Blu-ray discs contain both regular
subtitle tracks (dialogue only), and also SDH (Subtitles for the
deaf and hard of hearing) tracks, which contain both dialogue
and non-verbal audio cues.
How do I make a DVD
with closed captions or subtitles?
Closed captions
or subtitles can be added to a DVD project in the authoring
stage, using most professional DVD authoring programs like DVD
Studio Pro, Adobe Encore, Scenarist, etc.. Most consumer DVD
programs like iDVD or Toast do not support closed captioning or
subtitles.
Professional DVD authoring programs like those
listed above can import closed captions using a SCC (Scenarist
Closed Captions) file, which can be created by a number of
popular programs and caption service companies.
Some DVD
authoring programs have subtitle creation capability built-in,
although many users find it faster and easier to use software
specifically designed for rapid caption/subtitle creation. In
this case, the subtitling software will export either a text &
time script for the DVD authoring program (such as .STL for DVD
Studio Pro), or a time script with links to image files which
comprise each subtitle (.SST + .TIFs for Scenarist, .XML + .PNGs
for Blu-ray, etc.).
Can I add captions/subtitles
to an existing DVD?
Authoring a DVD is like baking a
cake. Once this disc is made, you cannot easily “unbake” it to
change the recipe. The best thing to do is to go back to the
source project which was used to author the DVD, add the
caption/subtitle tracks, and burn a new DVD disc or image.
Although it is technically possible to recover some (but not
all) of the assets from a burned DVD and then re-author it, this
is not recommended.
I have a video file that was captured
with closed captions. After authoring a DVD with this file, why
don't the captions work?
DVD stores closed captions
differently than analog or DV video, using data packets instead
of the "dots and dashes" in line 21. When your video file with
captions is compressed to MPEG-2 for DVD, the caption data will
not be preserved.
In most professional DVD authoring
programs, the only way to add closed captions to a DVD is to use
a SCC file. Fortunately, closed captioning software is available
that can easily extract the line 21 caption data from your
source video and convert it into a SCC file for DVD captions, or
even a subtitles file for DVD subtitles.
Another possible
alternative is to use a set-top box (STB) DVD recorder to record
your video via analog connections. Most STB DVD recorders will
internally convert the analog closed captioning signal into DVD
closed captions when recording a DVD.
How do I
create a SCC file for DVD closed captions?
Many
closed captioning programs, such as CPC's CaptionMaker and
MacCaption series, can output SCC files. The captions can be
created inside the closed captioning software, or they can be
retrieved and decoded from a video source that has already been
captioned.
Due to the nature of SCC files containing encoded
caption data, it is not feasible to create or edit them by hand.
The caption text is not in a human readable format, and the time
codes do not reflect the actual time codes of the captions due
to the buffering of the encoded data.
What are
some potential issues with playing closed captions from a DVD
player (assuming the DVD disc does have closed captions)?
The first and most important step is to make sure that the
closed caption decoder in your TV is turned on and set to the
right caption channel (usually CC1).
When using a set-top
DVD/Blu-ray player, the captions will not work if the player is
connected by HDMI or high definition component
(1080i/720p/480p). This is because HDMI does not support closed
captions at all, and component only supports captions at
standard definition (480i). Some DVD players now include closed
caption decoders, and internally render the captions into open
captions (burned into the image) before sending the video out
via HDMI or component. If you have such a player, the DVD player
menu or remote will have a button to turn the closed captions on
or off, and the TV’s caption decoder is not used. Not all DVD
players with HDMI/component have this capability, so you might
have to change your DVD player or switch to the composite or
S-video outputs instead.
In rare cases, some TVs do not
support closed captioning on all of the inputs, so you can try a
different input. Some display monitors which lack TV tuners do
not have caption decoders.
Another common issue is that many
software DVD players (for computers) do not support closed
captioning, or do not support it 100% correctly. For example,
most software DVD players cannot correctly decode roll-up or
paint-on closed captions. Some software DVD players can play
captions which appear at the very bottom or the top of the
screen, but not captions that are in the center area. There
continue to be many lingering issues with closed captions on
many software DVD players, so it is recommended to check your
disc on a real set-top DVD player.
Why aren't
the closed captions working on the DVD I authored?
The most common issue is a time code mismatch between the DVD
project and the SCC file which contains the closed captions.
Many NLE systems use a timeline that starts at 1 hour
(01:00:00:00) instead of at zero, and this timing is sometimes
preserved when you move into authoring the DVD.
There are
actually three timecodes in a captioned DVD: The project’s track
timecode, the MPEG video’s internal timecode, and the SCC
captions timecodes. A mismatch between any of these 3 timecode
systems can cause the captions to not work properly or at all.
If your SCC file captions start at zero but your DVD track or
MPEG file starts at 1 hour, then all of the captions will be 1
hour early. Conversely, if your SCC file captions start at 1
hour but the DVD track or MPEG-2 file start at zero, then all of
your captions will be 1 hour late (and if your DVD is less than
one hour, they’ll never appear at all).
For caption service
companies, a good recommendation is to always send your client
two SCC files: one that starts at 1 hour (01:00:00:00), and
another that starts at zero hours (00:00:00:00). Usually, one of
the two will work for the project, and this will help avoid
needing additional troubleshooting steps.
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